The present invention ralates generally to position, distance measuring, and navigation systems, and more particularly to improvements in such systems for golf course applications to provide greater accuracy in use by golfers to compute distances from present position to the green, the cup and other features of the hole being played.
In golf players are more comfortable and more likely to excel on courses with which they are familiar. It is customary for a golfer on a new or little-played course to seek to gain at least some familiarity with the layout of each hole before starting play. Armed with this information, the golfer can approach each tee box during play of the course, knowing, for example, whether the particular hole is a `dog leg left`, a `dog leg right`, or straight; the general locations of hazards, such as sand traps, bunkers, and water traps on the hole; and locations of range postings, if any, for calculating yardage from the golfer's location to the front and rear of the green, the pin (cup), a hazard, and a desired lay up position for the green approach shot.
Golf courses have traditionally made available course layout and feature information booklets in the pro shop, for just such purposes. Yardage markers typically are placed at sprinkler heads along each hole, to provide range information from that point to the center of the green. These serve as aids to the player, but they also contribute to slowing the pace of play of the course. Slow play has an adverse effect on the course's daily revenue, as well as on other golfers' enjoyment of the game.
Previously proposed improvements to golf course information and navigation systems have included use of buried electrical wires in various layouts on the course for interaction with mobile overland components (e.g., U.S. Pat. No. 5,044,634); and use of radio direction finding or triangulation techniques (e.g., U.S. Pat. No. 4,703,444 and U.S. Pat. No. 5,056,106). With more recent improvements in navigation and positioning systems, such as the government-sponsored Global Positioning System (GPS)--a technology now more than twenty years old--proposals have been advanced for use of other navigation systems, including GPS, on golf courses.
In co-pending U.S. patent application Ser. Nos. 08/423,295 and 08/525,905 of R. W. Rudow et al., filed Apr. 18, 1995 and Sep. 8, 1995, respectively, assigned to the same assignee as the present application ("the '295 and '905 applications"), improvements are disclosed in golf course positioning, yardage measuring and navigation systems utilizing differential GPS (DGPS) (see, for example, Blackwell, "Overview of Differential GPS Methods", Global Positioning System, vol. 3, pp. 89-100, The Institute of Navigation, Washington, D.C. (1986)). DGPS offers considerable error reduction in distance measurement over standard GPS, but still not quite adequate for the yardage accuracies demanded in the golf course setting.
The '295 and '905 applications provide enhancements, including unique filtering algorithms among other things, which offer considerably improved accuracy in measurements from a cart-based GPS receiver to the cup or other features, such as hazards and so forth, on a hole being played. A full color map of the golf course or individual holes or portions of a hole and all of their respective features to the extent surveyed and incorporated in the map database, are displayed on a video monitor in the cart. An icon such as a triangle representing the golf cart is also displayed on the monitor screen, in its real time position on the map of the course. By using a position selecting device proximate the monitor, the golfer can move a cursor arrow or pointer on the screen to a feature on the hole in play, such as the cup (variously also referred to as the pin or the flag), and request the system to calculate from the map database and display on the screen the real time yardage between the cart and the feature pointed to is, superimposed on the map. Such features as the tee box and pin placement may be changed each day by the course administrator but those changes are incorporated into the navigation system database by the administrator's base station so that the golfer is able to obtain an accurate measurement of the distance from the current position of the cart to the selected feature, armed with the most current data.
These and other features of the PROLINK.TM. yardage, course management and navigation system disclosed in the '295 and '905 applications (PROLINK is a registered trademark of Leading Edge Technologies, Inc. of Chandler, Ariz., the assignee of the latter applications as well as the present application) make it a superior golf cart-based (together with base station for course management) system with state-of-the-art graphics. An automatic zoom feature increases the selected target area resolution, such as to view the contour of the green or the details of a particular hazard. The user is able to make consistently better and faster club selection from the information concerning target distance and hole layout provided by the PROLINK.TM. system.
The system also allows a similarly equipped cart itself to be conveniently used for collecting survey data to map the layout of the course and its hole outlines, tee boxes, greens, cups, fairways, rough, cart paths, water hazards and sand traps, at the time the system is to be installed on the course. The collected survey data is processed, stored in memory as part of the data base, and available for later retrieval and display to aid in computing distances and indicate real time position of the cart and relative fixed positions of such features of the course. The course layout data is also useful for detecting the location of a golf cart within predetermined zones created using a zone detection algorithm, which additionally enables various system features such as automatic hole display on the cart monitor as the cart enters the tee box zone of a new hole, and automatic pop-up advertisements, promotional messages or golf tips when the cart is in transition from one hole to the next.
When the GPS signal is lost because the cart moves behind or beneath an obstruction, such as where the course is heavily treed, or hilly, or has on-course or adjacent buildings or other structures, with consequent interruption of line of sight to the GPS satellites, the GPS/DGPS system will go out-of-service and so notify the cart user with an on-screen message until signal is restored. Partly to overcome this problem, a dead reckoning system has been developed as the ACUTRAK.TM. golf course yardage, information and navigation system (ACUTRAK is a trademark of Leading Edge Technologies, Inc.), described in co-pending U.S. patent application Ser. No. 08/690,962 of J. R. Coffee et al., titled "Robust Golf Navigation System" filed Aug. 1, 1996 ("the '962 application"), which is commonly assigned with this application. A DGPS capability is provided in the ACUTRAK.TM. system, but only for purposes of periodically or intermittently calibrating the system. Apart from those distinctions, the ACUTRAK.TM. system shares many of the desirable attributes of the PROLINK.TM. system. The unique ACUTRAK.TM. dead reckoning (DR) guidance or navigation system tracks the distance moved by and the orientation of the wheels of the cart, extrapolated to the heading of the cart. The system is unaffected by inability to "view" a satellite navigation system, such as the GPS satellites, and operates with considerable accuracy with limited calibration during play. Calibration operates to remove the buildup of error in the wheel sensors, compass alignment, and other component-introduced error, which will again undergo gradual increase after a calibration as the cart is driven about the course during a round of play.
A co-pending patent application of J. R. Coffee, titled "Map-Matching Golf Navigation System" (Attomey's Docket 1304.014, hereinafter the "0.014 application"), filed on Mar. 31, 1997, and commonly assigned herewith, discloses a calibration technique for a modified ACUTRAK.TM. system which takes advantage of a cart path map database to substantially eliminate built-up DR error in circumstances where the cart is either restricted to the typically paved or otherwise well-maintained cart path found on most U.S. courses, or is likely to be on the path at least part of the time during play of each hole.
A significant percentage of golf courses in the United States invoke a "cart path only" rule which requires that the golf cart (the use of which is mandatory for play of those and most other courses) be restricted to cart paths, and that it not be driven on the fairway. In Japan, virtually all golf courses mandate a "cart path only" rule at all times. Even for many courses where the "cart path only" rule is not in effect at all times, it is a requirement on occasions when the course "manicure" may be affected by allowing carts to be driven on the fairway, such as where the course is wet from recent rain or snow or immediately after heavy sprinkler usage, or where the threat of inclement weather is imminent. Driving on the fairway can cause ruts which will adversely affect the path of the ball during roll after shots by players who follow the wayward cart driver, and generally tends to disrupt the care and etiquette of the course. Virtually all courses absolutely forbid driving a golf cart off the cart path in the vicinity of the tee boxes and the greens.
Since the golf cart, and not the ball, is provided with the guidance system, the position and distance measurements calculated by these systems are all with respect to the cart. Except in the case where an appropriate yardage measurement system is implemented in a hand held unit (e.g., with an incorporated DGPS receiver), which does not at present appear to have any surging demand for use on a golf course, unless the roving unit of the guidance system can be placed in close proximity to the ball the indicated yardage to the pin or other range points on the hole is not an entirely accurate representation of the yardage from the ball to the selected point. This is particularly true where the course imposes a "cart path only" rule, so that the cart is restricted from being driven off the cart path to a position proximate that of the ball.
It is a principal object of the present invention to provide a golf course navigation system for golf carts in which the yardage (distance) measurement is automatically made with respect to the position of the ball, or very nearly so, or can readily be corrected to so indicate by manual control, despite relatively frequent inability to position the cart itself in close proximity to the ball, such as when playing on "cart path only" courses.